摘要:

AbstractThe development of spinal cord circuitry in humans is poorly characterized, primarily because standard anatomical tracers must be actively transported, which requires living tissue. Intensely fluorescent lipid‐soluble tracers have largely eliminated this problem, at least for circuits that can be traced over short distances. We have, therefore, used the carbocyanine dye DiI (1, 1‐dioctadecyl‐3, 3, 3, 3‐tetramethyl‐indocarbocyanine perchlorate) to study the development of the dorsal root afferent projection to fetal human spinal cord between 8 and 19 weeks of gestation.We show here that the dorsal root afferents enter the gray matter of the spinal cord very early in gestation. By 8 weeks, a few axons have already reached the motor pools. These axons, presumably spindle afferents, traverse the length of the spinal gray matter in fascicles to reach different groups of motor neurons. As development progresses, these axons project to the ventral horn and branch in a restricted area in the intermediate zone as well as in the motor pools. Between 11 and 19 weeks of gestation, axons in the ventral horn elaborate boutons that appear to be in proximity to the motor neuron somata and their proximal dendrites.Other groups of axons penetrate the gray matter of the spinal cord all along the mediolateral extent of the dorsal horn. These axons descend to lamina IV, and then turn upward to terminate in laminae III and IV, arborizing primarily rostrocaudally. The time course of the development of these axons parallels that of the axons projecting to the ventral horn. On the basis of their laminar termination and patterns of distribution, we suggest that these are the central axons from dorsal root ganglion neurons that innervate low‐threshold mechanoreceptors in the periphery. Axon arborizations in laminae I and II were sparse, even at the latest developmental stages examined. It is unclear whether their specific connections have not yet developed or whether DiI does not diffuse well along these small‐caliber axons.This characterization of the development of the laminar specific projections of dorsal root ganglion neurons provides a foundation for studies of the expression of genes that may be implicated in dorsal root axon growth and branching in humans. © 1995 W

ISSN:0092-7317    

DOI:10.1002/cne.903540102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTaurine is an inhibitory amino acid that hyperpolarizes magnocellular neurosecretory neurons. To determine which cell types in the rat supraoptic nucleus contain taurine, we used a monoclonal antibody raised against a taurine conjugate. Preembedding immunocytochemistry was carried out at the light and electron microscopic levels using diaminobenzidine and gold‐substituted silver‐intensified peroxidase as markers. We report the presence of taurine in all cellular compartments of the supraoptic nucleus, except axons, with variable labeling intensities among the different compartments. Few cell bodies of magnocellular neurons were immunoreactive, but many distal dendrites and some proximal ones showed weak‐to‐moderate levels of immunoreactivity. Strong immunoreactivity was found over glial cell bodies and their processes, in particular in the ventral glial lamina of the supraoptic nucleus. Large astrocytic processes labeled with the taurine antibody included the endfeet participating in the glial limitans around capillaries and at the ventral surface of the hypothalamus. Other types of immunoreactive astropytic profiles were found scattered within the neuropil where these processes participated in different interactions with the neuronal elements of the supraoptic nucleus. Immunoreactive glial expansions, sometimes even the main process of the glial cell, engulfed axonal boutons. Other labeled glial processes were found between two magnocellular perikarya or closely apposed to the membrane of axonal boutons contacting the neuronal cell bodies. The frequent finding of closely apposed glial and dendritic elements bearing different levels of taurine‐like immunoreactivity suggests that exchange of taurine between those two compartments may occur. We propose that taurine could be released from supraoptic glia by a small decrease in osmolarity or by receptor‐mediated mechanisms during conditions of low hormonal (vasopressin and/or oxytocin) needs. Such released taurine could then act on presynaptic or postsynaptic sites, or both, to exert its neuromodulatory actions. © 1995 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903540103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractImmunohistochemical methods have revealed the transient neonatal expression of calcitonin gene‐related peptide (CGRP) in olivocerebellar compartments, and it has been hypothesized that this peptide plays a role in the development of olivocerebellar connectivity. Furthermore, the distribution of the CGRP binding sites in the cerebellar cortex also favors this hypothesis. In this study, the pattern of postnatal expression of α‐ and β‐CGRP mRNAs in the inferior olive (IO) complex was analyzed using in situ hybridization histochemistry with RNA probes complementary to specific sequences of α‐ and β‐CGRP mRNAs, and the results were compared with the pattern of CGRP immunoreactivity. High levels of α‐CGRP mRNA expression were found in specific subnuclei of the IO complex, i. e., the medial part of the dorsal fold of the dorsal accessory olive, the β nucleus, the dorsal cap, the caudal third of the medial accessory olive, and the rostral part of the dorso‐medial cell column; in the same subnuclei β‐CGRP mRNA was detected. The olivary distribution of the two CGRP mRNAs coincided with that of CGRP immunoreactivity. The expressions of α‐CGRP mRNA and CGRP immunoreactivity were restricted to the first 2 postnatal weeks, the peak being reached at the end of the first week; β‐CGRP mRNA was transiently expressed in the same olivary compartments, but only from postnatal day 6 to 9. In general, the α‐CGRP signal was also more intense than the β‐CGRP signal. The present findings indicate that the α‐ and β‐CGRP mRNA expression in the olivary complex is under developmental control and restricted to specific olivocerebellar compartments. The data provide a basis for the transient expression of a CGRP olivocerebellar compartment and further support the hypothesis of a role for CGRP in the complex postnatal cerebellar phenomena of connectivity reshaping and synap

ISSN:0092-7317    

DOI:10.1002/cne.903540104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractJun, Fos, and Krox proteins are inducible transcription factors contributing to the control of gene expression. The elucidation of their individual expression patterns in the nervous system provides new insights into the ability of neurons to react with changes of gene expression to external stimulation under physiological or pathological conditions. The expression of c‐Jun, JunB, JunD, c‐Fos, FosB, and Krox‐24 was investigated in the brain of untreated male Sprague‐Dawley and female BDIX rats by immunocytochemistry using specific antibodies.JunD immunoreactivity (IR) labeled the highest number of neurons, being present in almost all neurons of the brain. JunD was expressed at high levels in those areas that also exhibit c‐Jun, JunB, c‐Fos, and FosB‐IR, such as locus coeruleus, periolivary nuclei (ncl.), pontine and central gray, lateral lemniscal ncl., inferior and superior colliculi, leaflet of geniculate ncl., midline nuclei of thalamus, dorsomedial and paraventricular ncl. of hypothalamus, ncl. supraopticus, dorsolateral part of caudate putamen and lateral septal ncl. In contrast to the high number of JunD‐positive neurons, c‐Jun, JunB, c‐Fos, and FosB proteins were detected in rather low numbers of neurons in these brain areas; the rank of the number of immunopositive neurons was c‐Fos>JunB>c‐Jun>FosB. Particularly high levels of expression were observed for c‐Jun in medullary motoneurons, medial geniculate ncl., arcuate ncl., and dentate gyrus, and for JunB in the CA‐1 area of the hippocampus and islands of Calleja. The zinc finger protein Krox‐24 was expressed in many neurons of these brain areas, with only discrete Jun‐ and Fos‐IR; additionally, many intensely labeled nuclei were present in spinal ncl. of the trigeminal ventromedial ncl. of the hypothalamus and the CA‐1 area of the hippocampus. In the cerebellum, nuclear labeling was detected only for c‐Jun, JunD, and Krox‐24 in granule cells, JunD‐IR was also found in glial cells of gray matter and fiber tracts, whereas glial c‐Jun‐IR was observed only in fiber tracts. Apart from a weak JunD‐IR, some areas did not express Jun, Fos, and Krox proteins such as cuneate and gracile ncl., venterobasal. complex of thalamus, globus pallidum, and Purkinje cells of the cerebellum.Our data indicate that inducible transcription factors of thefos,jun, andkroxgene families show patterns of individual expression in untreated animals, thereby reflecting different mechanisms and/or thresholds for induction under p

ISSN:0092-7317    

DOI:10.1002/cne.903540105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractTwo channels of the cerebellothalamocortical system were investigated in cats by using cerebellar‐evoked synaptic responses and cortical‐evoked antidromic invasion of single thalamic cells. One channel arises in interpositus and dentate cerebellar nuclei and mainly projects through ventroanterior‐ventrolateral (VA‐VL) thalamic nuclei to cortical motor areas 4 and 6; the other channel arises in cerebellar fastigial nuclei and projects through ventromedial (VM) thalamic nuclei to more widespread cortical areas. The antidromic response latencies of VM neurons to stimuli applied to cortical areas 4 and 6 were longer (medians 2.8 and 3.0 msec, respectively) than the antidromic response latencies of VA‐VL neurons to stimulation of the same cortical areas (1.8 and 2.3 msec). This was a statistically significant difference, and it matched the longer latencies of fastigial‐evoked synaptic responses of VM cells (2.9 msec) compared to the response latencies of VA‐VL cells elicited by stimulation of interpositus or dentate nuclei (1.7 and 2.4 msec).These differences among thalamic nuclei relaying cerebellocortical impulses were corroborated by dissimilar effects exerted on the electroencephalogram (EEG) during high‐frequency (300 Hz) pulse trains applied to different deep cerebellar nuclei. The distribution of activated EEG patterns over the cortex depended on the stimulated site. Fastigial stimulation elicited the blockage of slow EEG rhythms and the appearance of fast oscillations (20–40 Hz) over widespread cortical areas in the proreus, pericruciate, and suprasylvian gyri. At variance, the activating influence of interpositus or dentate nuclei was restricted to the motor cortex. It is proposed that, besides their role in controlling the postural axial and proximal musculature, fastigial nuclei are part of diffusely activating systems. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903540106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractThe prohormone convertase (PC2) is expressed in the mammalian central nervous system (CNS) and has been shown to play an important role in the processing of certain neuropeptide precursors and prohormones at paired basic residues. Amphibian PC2 cDNA was recently cloned for the frogXenopus laevis, and both its sequence and its pituitary expression pattern were shown to be very similar to those of mammalian PC2. To investigate further the function of PC2 in the vertebrate CNS, we used in situ hybridization histochemistry to localize the distribution of cells expressing PC2 mRNA in the frog brain and the spinal cord. The distribution of PC2‐expressing cells was also compared with that of cells expressing thyrotropin‐releasing hormone (TRH) mRNA or peptide. PC2‐expressing cells were detected in specific nuclei that were widely distributed in the frog CNS. In forebrain, telencephalic PC2 mRNA was found in the olfactory bulb, pallium, striatum, amygdala, and septum, and diencephalic PC2 mRNA was seen in the preoptic area, thalamus, and hypothalamus. More posteriorly, PC2 cells were localized to midbrain tegmentum, the torus semicircularis, and the optic tectum, as well as the cerebellum, brainstem, and spinal cord. Despite this wide distribution, steady‐state levels of PC2 mRNA were clearly different in various brain nuclei. Regions with higher levels showed good correspondence to areas shown by others in frog to contain large numbers of neuropeptideexpressing cells, including TRH cells. On the other hand, not all brain areas with high levels of TRH mRNA had high levels of PC2 mRNA. Localization studies combining in situ hybridization and immunocytochemistry showed that, at least in optic tectum and brainstem, PC2 mRNA and pro‐TRH peptide coexist. These findings suggest that pro‐TRH is processed by PC2 in some, but possibly not all, brain regions. Thus, different converting enzymes may be involved in pro‐TRH processing in different brain regions. © 1995 W

ISSN:0092-7317    

DOI:10.1002/cne.903540107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractBirds have well‐developed basal ganglia within the telencephalon, including a striatum consisting of the medially located lobus parolfactorius (LPO) and the laterally located paleostriatum augmentatum (PA), Relatively little is known, however, about the extent and organization of the telencephalic “cortical” input to the avian basal ganglia (i. e., the avian “corticostriatal” projection system). Using retrograde and anterograde neuroanatomical pathway tracers to address this issue, we found that a large continuous expanse of the outer pallium projects to the striatum of the basal ganglia in pigeons. This expanse includes the Wulst and archistriatum as well as the entire outer rind of the pallium intervening between Wulst and archistriatum, termed by us the pallium externum (PE). In addition, the caudolateral neostriatum (NCL), pyriform cortex, and hippocampal complex also give rise to striatal projections in pigeon. A restricted number of these pallial regions (such as the “limbic” NCL, pyriform cortex, and ventral/caudal parts of the archistriatum) project to such ventral striatal structures as the olfactory tubercle (TO), nucleus accumbens (Ac), and bed nucleus of the stria terminalis (BNST). Such “limbic” pallial areas also project to medialmost LPO and lateralmost PA, while the hyperstriatum accessorium portion of the Wulst, the PE, and the dorsal parts of the archistriatum were found to project primarily to the remainder of LPO (the lateral two‐thirds) and PA (the medial four‐fifths).The available evidence indicates that the diverse pallial regions projecting to the striatum in birds, as in mammals, are parts of higher order sensory or motor systems. The extensive corticostriatal system in both birds and mammals appears to include two types of pallial neurons: (1) those that project to both striatum and brainstem (i. e., those in the Wulst and the archistriatum) and (2) those that project to striatum but not to brainstem (i. e., those in the PE). The lack of extensive corticostriatal projections from either type of neuron in anamniotes suggests that the anamniote‐amniote evolutionary transition was marked by the emergence of the corticostriatal projection system as a prominent source of sensory and motor information for the striatum, possibly facilitating the role of the basal ganglia in movement control.

ISSN:0092-7317    

DOI:10.1002/cne.903540108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractAlthough thalamic projections to the dorsal striatum are well described in primates and other species, little is known about thalamic projections to the ventral or “limbic” striatum in the primate. This study explores the organization of the thalamic projections to the ventral striatum in the primate brain by means of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) and Lucifer yellow (LY) retrograde tracer techniques. In addition, because functional and connective differences have been described for the core and shell components of the nucleus accumbens in the rat and are thought to be similar in the primate, this study also explores whether these regions of the nucleus accumbens can be distinguished by their thalamic input. Tracer injections are placed in different portions of the ventral striatum, including the medial and lateral regions of the ventral striatum; the central region of the ventral striatum, including the dorsal part of the core of the nucleus accumbens; and the shell region of the nucleus accumbens. Retrogradely labeled neurons are located mainly in the midline nuclear group (anterior and posterior paraventricular, paratenial, rhomboid, and reuniens thalamic nuclei) and in the parafascicular thalamic nucleus. Additional labeled cells are found in other portions of the intralaminar nuclear group as well as in other thalamic nuclei in the ventral, anterior, medial, lateral, and posterior thalamic nuclear groups. The distribution of labeled cells varies depending on the area of the ventral striatum injected. All regions of the ventral striatum receive strong projections from the midline thalamic nuclei and from the parafascicular nucleus. In addition, the medial region of the ventral striatum receives numerous projections from the central superior lateral nucleus, the magnocellular subdivision of the ventral anterior nucleus, and parts of the mediodorsal nucleus. After injection into the lateral region of the ventral striatum, few labeled neurons are seen scattered in nuclei of the intralaminar and ventral thalamic groups and occasional labeled cells in the mediodorsal nucleus. The central region of the ventral striatum, including the dorsal part of the core of the nucleus accumbens, receives a limited projection from the midline thqlamic, predominantly from the rhomboid nucleus. It receives much smaller projections from the central medial nucleus and the ventral, anterior, and medial thalamic groups. The shell of the nucleus accumbens receives the most limited projection from the thalamus and is innervated almost exclusively by the midline thalamic nuclei and the central medial and parafascicular nuclei. The shell is distinguished from the rest of the ventral striatum in that it receives the fewest projections from the ventral, anterior, medial, and lateral thalamic nuclei. © 1995 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903540109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

摘要:

AbstractEimer's organ is a tactile sensory structure found predominantly on the snouts of moles. It consists of a raised papilla of epidermis containing a column of cells associated with sensory receptors. This study compares the Eimer's organs of the hairy‐tailed mole,Parascalops breweri, the star‐nosed mole,Condylura cristata, and the eastern mole,Scalopus aquaticus, by using scanning electron microscopy and light microscopy. Eimer's organs are visible on the snout of the hairy‐tailed and the star‐nosed moles, but not the eastern mole. The Eimer's organs of the hairy‐tailed mole are similar in external appearance, distribution, and internal structure to those found in most species examined. The Eimer's organs of the star‐nosed mole and the eastern mole diverge from this basic form in seemingly opposite directions. The Eim&'s organs of the star‐nosed mole are more numerous, smaller, and highly organized units with a consistent pattern of neuronal terminal swellings within a cell column, below a thin keratinized epidermis. By contrast, the Eimer's organs ofthe eastern mole lie below a thick keratinized epidermis, are less organized in structure, and have no central cell column. The extreme differences between the Eimer's organs of the star‐nosed mole and those of the eastern mole may be the result of the habitat of each species, saturated mud allowing a more elaborate and delicate sensory apparatus in the star‐nosed mole and drier soil requiring a thick keratinized epidermis over the organ in the eastern mole. © 19

ISSN:0092-7317    

DOI:10.1002/cne.903540110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903540101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1995

数据来源: WILEY